The present invention pertains to a method for reading signal charges from a solid-state image pickup unit with either an improved resolution or reduced vertical integration density.
There has been known a solid-state image pickup unit including a photosensing section (matrix of photoelectric conversion elements), a charge transfer section, a charge transfer control section, and a mosaic microfilter arranged over the photosensing section. In the conventional pickup unit, each photoelectric conversion element is provided with a filter element corresponding to one of the three primary colors, red, green and blue.
Various patterns for the filter elements of the mosaic microfilter have been proposed. In one of these, known as the "Bayer" arrangement, red and green color filter elements are alternately arranged on the odd rows of photosensing elements in the photosensing section, and green and blue filter elements on the even rows. In this arrangement, red, green and blue color signals are thus independently read out by combining outputs from each respective two adjacent rows to thereby separately obtain the red, green and blue colors signals. Using this arrangement, a color image having a good resolution can be obtained, that is, a resolution substantially the same as that of a monochrome image sensing unit.
In the case where interleaved scanning is employed with such a color image pickup unit, the signals from respective adjacent rows numbers 2n+1 and 2n+2 are paired and employed for the A field of the output image, while the signals from respective adjacent rows numbers 2n+2 and 2n+3 are paired and employed for the B field (where n is zero or a positive integer). However, the use of interleaved scanning results in a degradation of the resolution in the vertical direction of the photosensing section. Improved resolution can theoretically be achieved by increasing the integration density of the device, but, in practice, increasing the integration density is difficult and accompanied by other problems.